Detachable bit for rock drills



Patented Mar. 1l, 1941 UNITED STATES DETACHABLE BIT FOR ROCK-DBILLS Ernest Craig, Falconbridge Township,

Ontario, Canada Application January z5, lago, sei-iai No. 315,478'

3 Claims.

This invention relates to rock drills of the type/ in Figures 1` to 8, the bit I, which may be of any which has adetachable bit secured at the end of the drill rod so that the bit may be removed in theshortest possible time by the driller and re- 5 placed with another bit.

The principal object of the present invention is to devise a novel construction of bit and shank steel which may be readily disconnected to enable the replacement' of the bit, but which will] i not be liable to be accidentally disconnected from the steel shank while in operation.

A still further and important object is to devise a structure of bit which may be manufactured at a cost which willpermit a one-time use, such costvbeing less than the cost of reconditioning and sharpening a used bit.

The principal feature of the invention consists in thevnovel construction of the shank and bit whereby the interconnecting socket and interilt- 20 ting portions are provided with circumferential curved surfaces which will effectively interlock through the rotative operation of the drill shank in the operation of the drill, and which may be ent invention.

Figure 2 is an elevational view showing the shank in position ready to be inserted in the bit.

Figure 3 is an elevational and part sectional.-

view showing the shank inserted in the bit..

Figure 4 is a bottom or plan view of the working face of the bit.

Figure 5 is a plan view of the top or socket end of the bit illustrated in Figure 3.

Figure 6 is a transverse section through the line 8-6 of Figure 3.

Figure '7 is a transverse section similar to the view illustrated in Figure 6 showing the shank and bit in their interlocked position` Figure 8 is a transverse sectional view of a shank and bit of a. slightly modified form..

Figure 9 is a longitudinal section of a modified construction of socket and bit.

It is found by those conversant with mining operations that the cost of resharpening drill bits runs into considerable sums of lmoney and it is highly desirable to provide a bit which will operate successfully in its service of cutting' rock but which can be discarded when it becomes too dull to function properly, so that the cost of resharpening service will be eliminated. x

In the form of-drill shank and bitlierein shown desired external form, is provided with a socket 2 which has an inner circumferential surface which is, as particularly illustrated in Figures 5, 6 and 7, a substantially spirally curved plane, 5 that is to say, the socket has a maximum radius,v extending from the point 3 which radius is graduallyreduced around the circumference until it reaches the point 4, and is preferably in the form of an Archimedes spiral. The mating end of the 10 ,drill shank is formed with acurved plane surface corresponding to that of the bit.

The amount of reduction of these radii may be varied in accordance with the character of -the n metal, the pressures applied to the drill and the speed of operation, and these curvatures will be designed so that the circumferential curves of both members will engage throughout substan tially their entire length and a secure interlock will occur between the inner circumferential surface of the blt socket and the external circumferential surface of the shank 5 of the drill steel i. The external peripheral contour of the end 5 of the drill steel will coincide with the contour of the socket 2 but the dimensions may be slightly 25,

less so as to permit the ready insertion of the shank into the socket, but upon a slight relative turning movement of the members thesurfaces will' be brought into interlocking engagement as' is illustrated particularly in Figure '7.

The Archimedes spiral is definitely characterized as presenting a curvature the radius of which increases uniformly with the angle and represents the locus of va point which is moved radially with uniform velocity while moving circumferentially with uniform velocity, as distinguished from cams or other forms of surfaces presenting curvatures which are segments of a circle or cylinder and which do not engage in continuous circumferential contact.

The shank portion 5 of the drill steel may be formed with its longitudinal walls substantially parallel to 'the axis, but, as illustrated particularly in Figure 3, the perimeter of the portion 5 maybeI corrugated circumferentially by one or 45 more corrugations l vso that the drill steel will present a plurality of circumferential lines of contact with the inner wall of the socket I, which is preferably of' uniform longitudinal conv. formation, thatis, having its Walls substantially parallel with the axis, though it may possibly be found desirable under certain circumstances and conditions to form circumferential corrugations within the socket. The element of cost however. being an important factor in respect to the present invention, the socket in the bit will preferably have its walls formed in a longitudinal straight line so that a very. simple stamping operation will form the bit.

'I'he bit as herein shown is of course provided with a central water-hole 8 to enable the flow of water through to the cutting surfaces.

In the form of the invention illustrated in Figure 8 the spiral surfaces are shown in duplicate,

that is to say, the innerv surface of the socket is formed with two half circumferentially curved yside wa1ls`9 which are engaged by correspondingly curved external peripheral surfaces on the drill steel shank, both of such inter-engaging surfaces being of the Archimedes spiral formation. Y

Figure 9 is shown to illustrate the fact that the spirally surfaced socket, may if desired, be formed in the. end of the steel shank I0, while the external curved structure may be formed on the portion Il of the bitto fit into the socket member of the shank.

It will be readily appreciated that the securing or the bit in position to the shank is very simple.

The parts are a loose fit, the spiral end of one member being inserted. in the socket of the other and jammed with a slight turn, and immediately the drill is put into operation it is rotated in the direction to force the decreasing radius surface of the socket against the increasing radius surfaceof the shank, or vice versa. The bit therefore remains securely locked during operation.

vexed so that a rounded contact surface is prol.

vided which will ensure theftransmission of the impact shocks fromthe drill steel to the bit with uniformity. A bit constructed as described may be manufactured at such low cost that it may be discarded after a "one-time" use. Further, bits so made have been proven to hold securely to the steel and to perform adequate service in operation.- i

What I claim as my invention is:

1. A rock drill comprising a bit and shank one of which is formed with a socket to receive and engage the end surface of the inserted member to transmit the impact shocks of the drill, the periphery of the inserted member and the surrounding wall of the socket being formed with interfitting spiral surfaces substantially parallel with the drill axis which continuously engage for the major part of their circumference to retain the impactsurfaces in contact. y

2. In a rock drill, a shank having its periphery at the end formed of a spirally curved plane, and a bit formed with a socket the bottom of which is the full diameter of the end of the shank and the inner periphery of which is a spirally curved plane, the spiral planes of both bit and shank each having a curvature the vradius of'which increases uniformly with the angle and represents the locus of a point which is moved radially with uniform velocity while being moved with uniform velocity circumierentlally, the spiral curved plane of the shank interlocking with the spiral curved plane of the bit on the rotation of the shank to retain the end of the shank in snug engaging contact With the bottom of the bit socket to transmit the impact shocks of the drill directly thereto.

3. A rock drill as claimed in claim 2 in which the shank member is formed with circumferential corrugations to present spaced peripheral contact surfaces to interlock with the spiral plane surface of the socket. I

ERNEST CRAIG. 

